28 August 1998

Compact maize must prove its value beats risk

By Jessica Buss

COMPACT maize varieties which stay green longer offer a better feed value than conventional varieties.

But research funding is needed to assess potential benefits and drawbacks of compact maize varieties under UK conditions.

So says CEDAR researcher Richard Phipps, who will speak at the compact and conventional varieties display at National Forage Maize Day on Sept 3 at CEDAR, Reading, Berks.

Compact varieties stay green longer in the growing season, so it is possible that stem digestibility will be higher than conventional maize.

Over the past 10-15 years crop maturity has been improved by breeders, allowing maize to be grown in the cooler northern parts of Europe. More recently, compact maize hybrids have been developed and are now available.

These compact varieties have potential to provide crops with higher feed value because they are shorter, increasing the proportion of ear to stover, or stem, harvested. This may result in a higher starch and energy content, improving feed value. A conventional plant at harvest is 60% ear and 40% stover, he says.

These potential benefits of compact maize must be proven to compensate for its lower yield, he stresses. "We need to find out the milk production achieved a hectare from home-grown high quality forage from both compact and conventional varieties. That requires trials on crop yield, quality, conservation and feeding. It may be that the different types of maize suit different situations.

"The ability to improve feed quality of home-grown forages must be taken seriously, as feed costs are of increasing importance," says Dr Phipps. To ensure optimum feed value of compact maize varieties, harvest strategies may need altering. When harvesting a conventional maize variety between 30 and 35% dry matter, it has a starch content of about 30%.

"But a compact stay-green maize may achieve a starch content of 30% at a lower dry matter, when grain is mature and the stover is still moist. Then overall crop dry matter would be lower, making it easier to compact in the clamp. Aerobic stability in the clamp could, therefore, be improved and feeding out losses reduced."

According to Dr Phipps it is difficult to decide the best time to harvest compact maize as it continues to look green and leafy when a conventional variety would be dying back. But grain maturity in a green compact variety could be similar to a conventional variety which has little green left.

Dr Phipps is hopeful that an easy method to decide when to harvest will be developed or adapted for the UK. In the US, a grain scoring system for conventional maize gives a good indication of starch content, he says. A milk-line forms on the grain as it matures and moves down the grain from the outside of the ear. When this line is about a third of the way down the grain it is 30% DM, at two-thirds it is 35% DM. When the base of the grain has turned black it is 45% DM, he adds. US producers use this to decide when to harvest maize for the required crop quality. &#42


&#8226 Potential for higher feed value.

&#8226 May produce lower DM yield.

&#8226 Stem could have improved digestibility.

&#8226 Improved aerobic stability?